Chosen Solution
I have a little mystery to figure out. I have my battery drained by a component connecting via fuse 31, namely: clock anti theft, immobilizer, instrument cluster power, buzzer, board computer, they are all on there. The draw is 0.25 amp for 60 seconds, then drops to 0.05 amp , which would be nice if it would remain there, but alas, it comes back to 0.5 amps after 60 seconds precisely. One local tech told me about the BMW board computer having a dedicated small watch battery which died and caused a similar effect in another BMW. It sound very plausible to me, given the regular nature of the intervals, one could nearly rule out a stuck relay or short…..or am I mistaken? So did anyone ever dig out the computer and find such a little battery which can be replaced? Or did anyone ever have a similar pattern and found the solution? Another weird thing is, that when I pulled the fuse, the car started up as if nothing was missing, except for the cluster no longer indicating its stuff. What gives here?
After reading just about anything I could find on the draining issue, I think I found a very slick solution: I will just reroute the power supply for that circuit from the current “always hot” fuse, and instead supply the power from one of the accessory fuses which only become hot when the key is on. The I only need connect the clock to an always hot wire,and I will lose my trip meter settings which I do not care about, and voila….
Hi @jurgenkoppen , Don’t know the answer but I was wondering if it were possible to unplug each component one at a time to see where the problem is emanating from. maybe start with the Board computer -low A35y as you suspect, which is located in the centre console. just a thought.
